Several deepwater oil and gas fields have been recently discovered which necessitate new methods and apparatus in order to produce them. The depth of the water at these locations may range from 2000 to 7000 feet of water. Two of the proposed methods for developing such oil and gas fields are known as ocean floor completions and the production facilities on tension leg platforms. In ocean floor completions, a well would be drilled from a floating vessel on the surface of the ocean subsequently be completed by hanging strings of casing and production tubing from a wellhead that is positioned on the ocean floor or at the mudline. In the second method, a tension leg platform floats in an anchored position on the surface of the water while conducting well drilling operations and subsequently production operations. In the later case, the wellheads are positioned on one of the decks of the tension leg platform and a production riser extends from each of the wellheads down to the ocean floor and downwardly into the formation to the hydrocarbon producing zone. In both cases, it is often desirable to remove some of the weight of the tubing pipe string from the wellhead by providing it with a tubing hanger which may be set deep in the well.
A second problem exists in the production of hydrocarbons, especially in gas wells, in that hydrates are often formed in the tubing string under the right combination of pressure and/or temperature. These hydrates tend to restrict the flow of hydrocarbons in the tubing string or block it altogether. Thus, it is desirable to add a chemical into the tubing string at a depth in the well which is below that at which hydrates form in the tubing string. Any of several chemicals which prevent the formation of hydrates and are well known to the art may be injected into the tubing string.